JPS63286879A - Image forming device - Google Patents

Abstract

PURPOSE:To effectively prevent lowering in transferring rate caused by contamination, by providing a destaticizing means closely to a transfer member and destaticizing a transfer member at the time of non-transfer. CONSTITUTION:A bias voltage of polarity opposite (plus in this case) to the toner is applied to a transfer roller 2 and the surface potential of the roller 2 is maintained at Va during the period of tA-tB after a photosensitive body is driven. During the period tA-tB, the toner image on the surface of the photosensitive body is transferred to a transfer material and, at the same time, a bias voltage of polarity equal to that of the voltage applied to the roller 2 is applied to a destaticizing needle 5 provided in the vicinity of the transfer roller 2. During the period of tB-tC after the transfer material passes through the transferring area, the bias voltage to the roller 2 is turned off and, at the same time, another bias voltage V of the same polarity as that of the toner is applied to the destaticizing needle 5 so as to destaticize the transfer roller 2. Accordingly, not only the transfer of the toner on the surface of the photosensitive body to the transfer roller 2, but also the attraction of the floating toner to the transfer roller 2 can be prevented effectively. Therefore, the contamination of succeeding transfer materials and the lowering in image quality can be avoided.

Description

Detailed Description of the Invention (1) Purpose of the Invention (Field of Industrial Application) This invention relates to image forming apparatuses that utilize an electrostatic recording process, such as electrostatic copying machines and printers, particularly transfer rollers, transfer belts, etc. The present invention relates to an image forming apparatus using an image forming apparatus.

(Prior art and problem to be solved B) A transfer member such as a transfer roller made of an elastic material with an insulating layer on the surface is disposed in contact with or very close to a moving image carrier, and the image is transferred to the roller or the like. An image forming apparatus configured to apply a bias, pass a sheet-like transfer material such as paper between the two, and transfer a transferable toner image formed on an image carrier to the transfer material. Already proposed.

In such an image forming apparatus, even if a bias is constantly applied during the image forming operation, or even if a bias is applied intermittently only when the transfer material passes, the transfer roller, etc. It is inevitable that the transfer material will be contaminated with toner and other foreign matter, which is difficult to completely remove.
Furthermore, there are other problems such as the toner and the like re-adhering to the image bearing member and deteriorating the image, and a reduction in transfer efficiency due to such stains on the roller and the like.

The present invention has been made to deal with such a situation, and is to actively prevent toner from adhering to the roller, etc. in an image forming apparatus that uses transfer members such as a transfer roller and a transfer belt. By doing so, it is an object of the present invention to provide an image forming apparatus that can always obtain high-quality images at a high transfer rate.

(2) Object of the invention (technical means for solving the problem and its operation) In order to achieve the above object, the present invention provides a transfer method in an image forming apparatus using a transfer member such as an insulating transfer roller or belt. The present invention is characterized in that a charge eliminating means is provided close to the member, and the charge is eliminated from the transfer member during non-transfer.

This configuration reliably eliminates the tendency for toner to adhere to the transfer member due to residual charge during non-transfer, and prevents contamination of the transfer member, smearing of the transfer material, reduction of transfer efficiency, and even Deterioration of image quality caused by these factors can be prevented.

(Description of Embodiment) Figure f51 is a side view of a main part showing an embodiment in which the present invention is applied to a copying machine equipped with a rotating cylindrical photoreceptor, and arrow A
The photoreceptor 1 is provided with a photoreceptor 1 that rotates in a direction, and an elastic transfer roller 2 that is disposed in contact with or very close to the photoreceptor 1 and that has at least the surface formed of an insulating material.

It is assumed that the transfer roller 2 is configured to run synchronously at a portion facing the photoreceptor by appropriate means.

Transfer material (not shown) supplied from a cassette (not shown), etc.
arrives at the transfer site where the photoreceptor 1 and the transfer roller 2 face each other in time with the toner image formed on the surface of the photoreceptor by the registration roller pair 3 and progressing as the photoreceptor rotates, and at this time, As will be described later, the toner image is transferred to the transfer material by the action of a transfer roller to which a bias is applied with a polarity opposite to that of the toner.

It is assumed that the transfer material is then separated from the photoreceptor and transported to a fixing site (not shown) by the transport path 4.

As is well known, around the photoreceptor 1,
It goes without saying that means required for repeated image formation, such as a latent image forming means, a developing means, and a cleaning means, are provided, but since they are not directly related to the present invention, they are all omitted.

In such an image forming apparatus, the transfer roller 2 includes a core bar 20 made of a rigid material such as metal, an inner layer 2b surrounding the core bar 20 and made of an elastic material such as urethane rubber or silicone rubber with or without bubbles. Urethane rubber is composed of an outer layer 2a made of an insulating and highly wear-resistant material, and the outer layer has a thickness of 0.1 to 2 mm and a hardness of 30 to 80°. do.

Further, in order to support the transfer material with a predetermined pressure between the transfer roller 2 and the photoreceptor 1, it is assumed that the transfer roller 2 is elastically biased toward the photoreceptor by a spring or the like.

The inner layer 2b does not need to be insulating; rather, it is more convenient to be conductive in order to maintain a uniform surface potential of the insulating outer layer 2a, and in order to make it conductive, Conductive particles such as carbon may be dispersed.

In the vicinity of the transfer roller, a charge eliminating needle 5 is arranged to remove the electric charge from the transfer roller as necessary. 0 In the figure, reference numeral 6 indicates the transfer roller, a power source for applying voltage to the charge eliminating needle,
Reference numeral 7 denotes a control circuit that controls voltage application to the registration roller 3, the static elimination needle 5, and the transfer roller 2 in accordance with a timing control sequence signal.

Figure 2 is a plan view showing the shape of the static elimination needle, which is made of a conductive plate made of stainless steel or bronze plated with nickel, and has many serrated ends formed on one edge of the conductive plate. , the tip thereof is placed at a distance of about 2 to 4+a+e from the surface of the transfer roller.

In addition to the above-mentioned static-eliminating needle, for example, stainless steel fibers planted on the edge of an aluminum substrate can be used as the static-eliminating means for the transfer roller, and this can be used to rub the surface of the transfer roller. Static electricity can be eliminated by this.

FIG. 3 is a timing chart showing the relationship between the transfer operation and the charging characteristics of the transfer roller.

After the photoreceptor is driven, a bias of polarity opposite to that of the toner (in this case, positive) is applied to the transfer roller for a period of time t^ to tH to maintain the surface potential of the transfer roller 2 at Va. The toner image on the surface of the photoreceptor is transferred to a transfer material.

At this time, a bias having the same polarity as that of the transfer roller is also applied to the static elimination needle, thereby contributing to maintaining the surface potential of the transfer roller and improving the transfer efficiency.

Then, the time 1 −1 after the transfer material passes through the transfer site
During this period, the bias of the transfer roller is turned off, and a bias of the same polarity as the toner is applied to the static elimination needle to eliminate static electricity from the transfer roller. As a result, the toner existing on the surface of the photoreceptor is transferred to the transfer roller. It is possible to effectively prevent the floating toner from being attracted to the transfer roller as well as from being transferred, and it is therefore possible to avoid the situation where the subsequent transfer material is stained or the image quality is deteriorated.

Note that when the photoreceptor is stopped, in order to prevent damage to the photoreceptor, it is preferable to reduce the bias applied to the static elimination needle at time t 2 immediately before the photoreceptor stops.

With this configuration, as described above, it is possible not only to prevent the transfer roller from being contaminated, but also to improve the transfer efficiency, making it possible to stably obtain high-quality images.

In the above-mentioned device, a registration roller is used to control the bias application to the static eliminating needle, but it is also possible to use a jam detection means that is normally incorporated in this type of device.

Further, it is not a problem to separately provide a cleaning means such as a cleaning blade to the transfer roller, and when removing static electricity from the transfer roller, it is also possible to simply ground the static elimination means without actively applying a static elimination bias. However, it is easy to understand that it is also possible to apply an alternating current bias.

Furthermore, although the present invention is applied to a copying machine), the present invention is not limited thereto, and can be applied to various image forming apparatuses, and not only to transfer rollers. Of course, it can also be used as a belt-shaped transfer member.

(3) Effects of the Invention As explained above, the present invention provides an image forming apparatus in which a transfer member such as a transfer roller is disposed close to an image bearing member, in which a static eliminating needle is disposed close to the transfer member to prevent transfer. In some cases, since the charge removal needle is configured to apply a bias of the same polarity as the toner, it is possible to actively eliminate residual charges from adhering to the transfer roller and maintain its surface in a clean state, thereby preventing contamination. It is possible to effectively prevent a decrease in the transfer rate due to this, and it is also possible to stably obtain high-quality images without back staining over a long period of time.

[Brief explanation of the drawing]

Fig. 1 is a side view of essential parts showing an embodiment in which the present invention is applied to a copying machine, Fig. 2 is a plan view of the static eliminator described above, and Fig. 3 explains the timing of bias application to the static eliminator needle and transfer member. This shows a timing chart. DESCRIPTION OF SYMBOLS 1- - fist photoreceptor, 2 fist φ transfer roller, 3... registration roller pair, 5... static elimination needle, 6... bias power supply, 7... control circuit. Figure 1 Figure 2

Claims (1)

[Claims] An insulating transfer member is brought close to or in contact with the image carrier,
In an image forming apparatus that transfers a toner image on the surface of an image carrier to a transfer material by passing a transfer material between the two, a charge eliminating means is provided in proximity to the transfer member to eliminate charge from the transfer material during non-transfer. An image forming apparatus comprising: